206 Proceedings of the Royal Physical Society. 
in accounting for their preservation on any hypothesis, until 
an accidental phenomenon enabled me satisfactorily to account 
for it. 
While preparing chloride of gold, I had occasion to expose 
to the action of nitro-muriatic acid many small articles of 
jewellery which had been chased and variously-fashioned. 
After exposing them for many hours in the usual bath at the 
proper temperature, I was astonished to find that none of the 
articles had changed either in shape or size, although the 
solution showed the proper quantity of gold had been dis- 
solved. After decanting the acid, and washing well the 
jewellery with distilled water, and again adding a fresh quan- 
tity of aqua regia, I found that no further portions of gold 
were dissolved, but that the articles still retained their form 
and size. Some of the rings, which were chased in high re- 
lief, exhibited, as when put into the flask, every mark of the 
workman's tool. The mystery was soon unriddled; the jewellery 
had all been alloyed largely with silver, every atom of which 
had been changed into a chloride, and as each atom of gold 
was dissolved, it was replaced by an atom of the worn silver, 
and so the form of each article was retained as when first put 
into the flask. On analysis, it was found that no particle of 
gold was left— all was converted into chloride of silver. This 
fortunate experiment at once enabled me to perceive, that when 
a ligneous atom was removed from a fossilising tree, an atom 
of silica was deposited, and hence the perfection with which 
the most minute structure was preserved. 
This being the last meeting of the Session, the Society 
adjourned to the commencement of next Winter Session, 
